One of the problems associated with air-dropped sonobuoys or other type air-dropped apparatus is the problem of the release of the drogue or parachute once the sonobuoy has impacted the surface of a body of water. The reason that it is desirable to release the drogue is that its lines may become entangled with the sonobuoy and thereby cause the sonobuoy to be dragged by the drogue due to either local current or wave action. In the case of sonobuoys which transmit subsurface information to overflying aircraft, it is important to maintain the vertical orientation of the sonobuoy so that the range of the sonobuoy will not be diminished. It will be appreciated that if the sonobuoy is pulled from its vertical position to an essentially horizontal position it is likely that the antenna carried by the sonobuoy will be submerged beneath the surface of the ocean and thus the range of the sonobuoy will be limited.
In the past there have been many complicated release mechanisms some of which have been cumbersome and unreliable due to jamming of some of the elements making up the release mechanism. Of course if the drogue is not reliably released, the sonobuoy may not either deploy its payload or transmit subsurface information and additional sonobuoys must then be deployed.
Moreover, the range of impact velocities over which the release mechanism must work varies greatly in that sonobuoys may be ejected from as little as twenty five feet over the surface of the ocean from a helicopter or from as much as 50,000 feet, when the sonobuoys are released by high-flying jet aircraft. Thus, in order for the release mechanism to be universally applicable it must operate over a wide range of impact conditions. Not only must a wide range of impact conditions be accommodated but also the swinging motion of the sonobuoy as it descends may cause the sonobuoy to enter the ocean at other than a vertical orientation. In some instances the entry angle of the sonobuoy may be as much as sixty degrees from the vertical, which in some instances may cause the release unit to malfunction due to canting of the release apparatus.
The foregoing problems in reliability are solved by the subject invention in which the drogue for the air-dropped article is attached to a spring-loaded release unit which is carried at the top surface of the sonobuoy, with an ejection spring positioned between the release unit and the top of the sonobuoy to eject the release unit upon water impact. A second spring is provided which acts normally as a detent to prevent ejection and is freed upon impact by the momentary downward travel of the release unit against its ejection spring as a result of the impact to permit ejection of the release unit. Reliability of the release unit is in part achieved by its simplicity of operation and in part by its light weight.
In one embodiment the release unit is placed over a central post which projects above the top surface of the sonobuoy. The post projects through a central bore in the release unit and the release unit is held in place by a U-shaped release spring at the top of the release unit. The U-shaped spring serves as a detent coacting with an annular groove at the top of the post. When the release unit is in place and is spring loaded from beneath, as by an ejection spring placed between the release unit and the sonobuoy, the U-shaped spring prevents upward movement of the release unit. In assembling the unit, the U-shaped spring is compressed around the post in the annular groove and is held in place and restrained against outward movement by pins or the like which project upwardly from the top surface of the release unit adjacent the ends of the U-shaped spring. Upon water impact the weight of the release unit depresses the ejection spring and the release unit translates downwardly on the post. As the release unit moves downwardly the pins move downwardly and out of engagement with the ends of the U-shaped spring. As a result, due to the spring tension the U-shaped spring springs open and out of engagement with the annular groove which results in the upward ejection of the release unit away from the sonobuoy.
Put another way, upon impact the mass of the release unit momentarily depresses the ejection spring and the unit moves downwardly moving the pins away from the ends of the U-shaped spring. The U-shaped spring then pops open and away from the notched post thereby unlocking the release unit. Immediately after impact the release unit is propelled by the ejection spring upwardly and off of the post away from the sonobuoy carrying the drogue with it.
It is an important feature of this invention that after the release unit and drogue are propelled away from the sonobuoy, the weight of the release unit causes the drogue to sink thereby carrying the drogue to the bottom of the ocean and away from the sonobuoy so that the sonobuoy cannot foul in the drogue or its attaching strands.
It is therefore an object of this invention to provide improved release mechanism for drogue apparatus associated with air-dropped articles which impact the surface of a body of water.
It is another object of this invention to provide a reliable release mechanism for sonobuoys ejected above the surface of a body of water in which release is effectuated upon water impact.
It is another object of this invention to provide an impact release unit which is spring-biased and locked into place with another spring member which is released upon the downward travel of the release unit at impact.
It is a still further object of this invention to provide a reliable impact release mechanism including the combination of a spring-biased release unit and a spring utilized as a detent locking member in which the spring detent is released at impact due to the translation of the release unit as a result of the impact.
These and other objects will be better understood in connection with the remainder of the specification in conjunction with the drawings in which